BestBlog: Developing and Refining a Chassis For The American Market

As many of you have seen, last season I was fortunate enough to get an offer to participate in the SKUSA SuperNats with factory support from BestKart. The goal was to take the first steps to introduce this chassis brand to the American market. While our results at that event were not what we were hoping for, we did a lot of good work and learned a lot about the kart in just a few short days. At the end of the week we discussed further collaborations with the BestKart factory. So this season I am again lucky to be offered the opportunity to continue that relationship and race with BestKart factory support with the help of @Paul_Montopoli and Prodigy Motorsports at the Stars Championship Series and other select events, as well as plenty of testing. Part of my duties as a development driver are to share my insights and thoughts on the chassis itself, what all the different setup changes do, and highlight the progression we go through as we continue to develop the kart for the American market, which is what I’m going to be doing in this blog. We want potential customers to have a good idea of how the chassis works and what kind of setup changes we are making to get it dialed into each track and condition. I often bemoan the “secret setup” changes that other teams or chassis keep hidden, so we want to make sure that anyone who is interested in driving a BestKart will have all the knowledge and tools they need to make it work in any condition.

I already outlined some of the changes we made to the kart when we had it in Vegas, which you can read about here: SKUSA SuperNationals 26 - TJ Driver Diary

Yesterday I was able to get the BestKart F03 out to Dousman for the first time and flog it for a couple sessions on my home turf, which gave me a really good comparison to past chassis I’ve driven now that I was on familiar ground. The BestKart F03 is a 30/32mm chassis with a design based on the successful Kart Republic KR2. It is made 100% in BestKart’s factory, using components made in-house as well as AMV components and wheels you find on other karts. The kart functions very similar to the KR. It runs without a front bar for the most part, and the rest of the frame is fairly flexible. The kart I currently am testing is the same kart Paul drove in a few club races and at CKNA and Stars Charlotte. BestKart considers this their “medium-stiff” frame, though it does still feel like it’s on the softer side compared to other chassis.

For yesterday’s session, I had AMV 3F wheels and used MG Red SH2 tires. Track was pretty slick and dusty and temps were in the low 70s with low humidity. I only had time for a couple sessions as I was coaching the rest of the day. The setup on the kart had already been tweaked on by Paul at his previous events, so I started where he had it just to get a feel for everything and shake it down. Basically the setup was a bit wider on front track, no front bar, max caster, low front ride height, high rear ride height, 1390mm rear track, C+ (stiff) axle. My first session was a 12 lap session and my best lap was 39.6. There was more time in it, but I’m rusty and was a little sloppy in my driving. Still, this lap was fast among the other KA Seniors there on that day. I hadn’t sat in a kart since November. The kart balance was really good; I was impressed. Super neutral, no real over or understeer in fast or slow corners, and it felt like the kart released off the corner really well. Sometimes when the kart feels that neutral/well balanced, it isn’t fast as it typically means the inside rear isn’t unloading enough. Coming from OTK that’s certainly the case. The OTK really needs a high initial hike of the inside rear to carry it through the corner. Initially the BestKart feels like it loads up more progressively and is able to flex enough to keep the inside rear unloaded without as much input/mechanical jacking on entry. It was reassuring that the direction we were tuning in Vegas before we totaled the kart, was seemingly the right direction, as the setup I ran yesterday was basically where I was headed on setup in Vegas before the wreck.

Unfortunately my day was cut slightly short due to an issue with the brakes. There was air in the system somewhere. I tried to bleed them but it made no difference, and the pedal was getting soft halfway through the run, so it may have a nicked seal or something. I need to inspect further.

Other than that, I was happy with the first outing on a proper circuit. It was hard to get a good judgement on the kart in Vegas since it was an unfamiliar circuit and a different surface than we are used to. But on a real race track, the kart felt very strong.

I am hoping to test all the axles next time I go out and report back. Not a ton of info right off the bat here, but I wanted to at least get the blog started and post my experience since I had a few friends ask how the kart was. More to come!

For more information on the BestKart, feel free to comment, PM or email myself or @Paul_Montopoli and we’d be happy to answer for you.

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Good work mate. The fun days testing & developing chassis’.

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@tjkoyen Still waiting on my chassis to test it in Europe :eyes: :grinning:

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Tested axles yesterday at Badger. Weather was 75F and sunny, track conditions were low grip with minimal rubber on the track.

The kart was setup with the C+ axle (stiff+) as it had been run by Paul at Stars and CKNA. Running the C+ gave very good traction and balance on the green surface at Badger. I then switched to the B axle (standard), which was two steps softer. The softer axle provides more flex in the rear of the kart, allowing the inside rear wheel to unload and lift easier. The trade-off is that it doesn’t plant the outside rear tire as hard, so at max load I noticed a little slip in the rear. However there was a noticeable difference in the effort required to initiate rotation in turn-in. The softer axle required less aggressive initial turn-in as the inside rear wheel unloaded easier.

TLDR:
On the BestKart, the softer axle will “free up” the rear of the kart, allowing for more lift at the cost of less side bite or dig. Similar to a softer seat or removal of seat struts.

The stiffer axle will “lock down” the rear of the kart more, providing more stability and traction at the cost of less flex and inside rear wheel lift.

  • Softer axle for high grip tracks.
  • Stiffer axle for low grip tracks.

Also axle changes should look like this:
200w

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Not gonna lie that kind of axle movement is satisfying. Is that a two or three bearing axle. I’m assuming three and I just can’t see the middle one.

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It’s three but I just don’t have the third bearing in right now.

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Can’t wait to get that baby back on track at NCMP for Stars round 2. Hopefully with all this testing and development I will give @DIG78x and gang a better run for their money.

Looking forward to racing and downing brews with @ChrisHoran, @Andy_Kutscher, @Muskabeatz, @CrocIndy, and @tjkoyen.

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For those that are interested, please reference this link for the axle chart.

Slide thru the images to see the chart.

And no, I don’t know what the numbers mean.

bestkart uses AMV axles.

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Looking forward to it! This development is really fun to follow along with too.

@tjkoyen is the right man for the job too!

Interesting take! Would you say that’s opposite of your OTK playbook?

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That is definitely opposite of our OTK experience!

Yes, the axles on the BestKart seem to tune more “conventionally” compared to the OTK philosophy. I also am aware I took two steps on the axle chart here and went from the super stiff to the medium, but the difference was definitely noticeable. On the OTK I always found the axles to be more subtle in how they change the kart’s attitude.

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why do karts behave so differently in regards to the rear axle effect on handling?

All the frames seem to have similar geometries now.

Actually, the full meaning is printed right there on the page!

AMV axles go from weakest to strongest! The strongest “hardest” axles take more force to yield than the weaker “softest” axles. Once the steel starts yielding, the force versus deflection curve will drop off, giving in many cases a spring with a near-zero rate.

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according to the test Larry H did, the hard and neutral axle deflected the same amount, under the same load
Are you saying he should’ve ran the test with a much heavier load?

Do different stiffness axles do anything? - Chassis Setup, Tires & Handling Forum - KartPulse - Presented by TBD

the AMV chart list the different yield index of axles, stiffer being higher yield index, my understanding is yield index is the point where steel tubing begin to deform permanently, and tensile strength is where it breaks.
If this is correct, then normal kart driving should never reach even the yield index.

It would be interesting to see a chart of the deflection curve of the different axles up until the yield index limit.

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TJ, i wonder if you try the Tony Kart axles in the Bestkart, does the tuning relationship with axle revert back to the OTK style?

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Would definitely be a good experiment! I will have to dig out some OTK axles.

Geometries between chassis are similar but there are lots of subtle differences in design. Combined with tubing material, wall thickness, tubing diameter, heat treatment, and components there are lots of opportunities to make a kart work or tune differently.

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